This Phase I application offers a novel approach to the development of a recombinant immunotoxin consisting of a tumor antigen (EGP-2)-specific single chain antibody fused to the enzyme glucose-oxidase (GO). The goal of this proposal is to achieve high level expression of this immunotoxin in the yeast, saccharomyces cervisiae, and to determine the feasibility of its use as an anticancer agent. Preliminary evidence indicates that this GO-based immunotoxin exhibits specific binding to the EGP-2 antigen and enzymatic glucose oxidase activity (hydrogen peroxide production). Proposed in vitro studies will examine the effect of yeast produced immunotoxin on the survival of normal and EGP-2 positive human colon cancer cells. This revised Phase I application also includes limited in vivo studies to examine the anticancer effects of this immunotoxin against human colon cell tumors in a mouse xenograft model. Upon completion of the Phase I aims, we will establish proof of concept for the effectiveness of this novel GO-based immunotoxin produced in yeast Phase Il will further develop and optimize the expression and low cost production of other immunotoxins, and will demonstrate their therapeutic potential by in vitro and in vivo tests for the development of superior immunotherapy systems. PROPOSED COMMERCIAL APPLICATIONS: Immunotoxins and monoclonal antibody-based therapies are rapidly being developed by biopharmaceutical industries and the market potential for these drugs will be over $6 billion by year 2000. This Phase I proposal addresses two important issues for this market: development of novel immunotoxins as anti-cancer agents and optimization of low cost systems for the production of immunotoxins that will help reduce healthcare costs.